There are many types of welding power supplies and welding processes. One welding process is referred to as pulse welding. Pulse welding generally consists of the output current alternating between a background current and a higher peak current. Most of the transfer (of the wire to the weld) occurs during the peak state.
There are many known power supplies used for pulse welding. While some of them perform well, one of the more challenging aspects of pulse welding is the start of the process. A number of problems plague starts of the pulse welding process. Among the problems are flare ups, where the wire flares near the tip, or where a piece of wire is violently exploded away from the weld. Another problem includes the arc extinguishing.
Poor starts are particularly troublesome for short (length) welds. For example, three attempts to start a one inch weld will extend nearly the entire one inch. Also, poor starts can lead to shorter tip life. With aluminum starts in particular, the wire can get stuck in the tip and at the start the wire gets burned back up to the tip and damages the tip. Damaged tips can reduce the productivity of the process, as the user needs to stop and replace the tip. Prior art systems claim to be able to make 60,000 consecutive starts using a single tip, but it is preferable to get even more starts from a single tip.
One cause of poor starts is a large ball left at the end of the wire left from the end of a previous weld. Larger balls require more energy to melt. More energy increases the volatility of the start. Also, the variations in ball size make consistent starts difficult. U.S. Pat. No. 6,023,046, commercially available as Sharp Start™ prevents balls from forming at the end of the weld.
Even if the large ball is prevented poor initial contact, improper run-in speed, hot spots, the wire sticking to the tip, and slow current ramps can cause poor starts. Power supplies have not adequately addressed these problems. Accordingly, a pulse welding system that provides for a robust and repeatable starts is desirable. Preferably it will provide for long tip life.